In recent years, compactness, high output, and high quality have been required in rotary electric machines such as electric motors or generators. In high-output rotary electric machines of this kind, since high voltages are applied, it has been necessary to increase insulation performance by increasing the thickness of insulating material that covers conductor wires that are mounted into the armature core because electric potential differences that arise between the conductor wires, particularly in coil ends, are increased. However, when the thickness of the insulating material is increased, the ratio occupied by the conductor wires inside the slots (the space factor) is reduced, reducing the efficiency of the rotary electric machine.
In consideration of such conditions, conventional rotary electric machines have been proposed in which thin insulating coatings are disposed on rectilinear portions of conductor wires that are housed inside slots, which have smaller electric potential differences, and thick insulating coatings are disposed on coil end portions, which have larger electric potential differences, to increase space factor inside the slots while ensuring required insulation performance in the coil end portions (see Patent Literature 1, for example).